Sharpening a knife relies entirely on abrasion to remove material until the steel apexes at a fine point. The abrasive material, whether on a stone, sandpaper, or strop, determines how much metal is removed and the final quality of the cutting edge. Choosing the right abrasive size is the most important factor in achieving a functional and durable edge. The size of the abrasive particles dictates the speed of material removal and the resulting finish, moving from a rough scratch pattern to a highly polished surface.
Understanding the Sharpening Grit Scale
The term “grit” refers to the size of the abrasive particles embedded in a sharpening medium, such as a whetstone or diamond plate. Grit numbers are inversely related to particle size; a lower number signifies larger, coarser particles that remove material quickly, while a higher number indicates smaller, finer particles that produce a smoother finish. This sizing is traditionally based on a mesh count, representing the number of abrasive grains that fit within one linear inch of screen during the manufacturing process.
The Japanese Industrial Standard (JIS) is the most common system used for water stones and is frequently encountered by knife sharpeners. Other standards, such as the European FEPA-F and the American ANSI, also exist, and their grit ratings can diverge significantly, especially at the finer end of the spectrum. For example, a stone rated as 1000 grit in the JIS standard may not equate precisely to a 1000 grit stone rated under a different system.
Choosing Grit Based on Knife Damage
The appropriate grit choice is determined exclusively by the current condition of the knife’s edge and the desired outcome. The entire grit scale can be functionally divided into three categories, each serving a specific purpose in edge maintenance and restoration. Selecting the correct starting point prevents unnecessary wear on the knife and speeds up the entire sharpening process.
Coarse Grits (100 to 600 JIS)
Coarse grits are reserved for edge repair and significant reshaping. These stones feature large, aggressive particles designed to rapidly grind away substantial amounts of steel. They are necessary for fixing chips, removing deep nicks, or when a severely dull blade needs a completely new bevel angle established. The scratch pattern left by these grits is deep and highly visible, making them unsuitable for finishing an edge.
Medium Grits (800 to 2000 JIS)
Medium grits are the workhorses used for primary sharpening and routine edge maintenance. This range is where the initial cutting edge, or apex, is formed after the coarse work is complete. A common starting point for a moderately dull knife is a 1000-grit stone, which effectively refines the coarse scratches and establishes a uniform, functional edge. The scratches left by these stones are shallow enough to be easily removed by the next step in the progression.
Fine and Polishing Grits (3000+ JIS)
Fine and polishing grits, which begin at 3000 JIS and can extend past 8000, are used for final refinement and mirror polishing. These extremely small particles remove minimal material while smoothing the microscopic saw-tooth pattern left by the medium stone. Finishing on a very fine grit creates a highly polished edge that appears reflective and provides a smooth, clean cut, which is often preferred for kitchen and precision knives.
The Essential Sharpening Progression
Achieving a highly functional edge requires a sequential progression through grits, always moving from coarse to fine. This systematic approach ensures that the deep scratches left by one stone are completely removed by the next, slightly finer stone. Starting with the lowest grit needed to repair the edge damage, the goal is to create a complete and consistent apex along the entire length of the blade.
The formation of a burr, a thin wire of metal that curls over the edge, is the physical indicator that the abrasive has reached the apex on one side of the blade. Sharpening continues on the first stone until a continuous burr is felt on the opposite side, confirming that both sides of the edge have met. Once a burr is established, the transition to the next finer stone can occur, with the first few passes on the new stone focused on removing the burr created by the previous, coarser grit.
This process of forming and then reducing the burr is repeated on each successive stone until the finest chosen grit is reached. The burr becomes progressively smaller with each step, eventually becoming a microscopic “wire edge” that must be completely removed for the edge to be stable. The final step in the progression is often stropping, which involves drawing the blade over a material like leather or balsa wood, typically with a very fine abrasive compound. This final trailing-edge motion removes the last remnants of the burr and lightly polishes the apex, maximizing the sharpness and edge stability.